Our previous assay for bradykinin in urine and plasma was re-evaluated. Measurements of bradykinin in urine are accurate for urines without proteinuria. In the presence of proteinuria additional cross-reacting material may necessiate further processing of urine prior to assay. Frequent voiding is necessary to minimize intravesical destruction of bradykinin. The major problem in the measurement of bradykinin in plasma is one of specificity. Experiments are now in progress in which we compare several methods of preparation to results obtained with bioassay. Bradykinin adherence to plastic tubes was re-evaluated. We have improved considerably our assay for bradykinin in plasma in terms of accuracy and sensitivity. This should help us to better understand the role of the kallikrein-kinin system in health and disease.